1. Field of the Invention
The present invention relates to a fallboard opening and closing device used in a keyboard instrument, such as a piano or an organ.
2. Description of the Related Art
Conventionally, as described in Japanese Patent Application Laid-Open (Kokai) Publication No. 2003-263151, a keyboard instrument is known that has a structure in which a fallboard is attached to an instrument case by a hinge that allows it to open and close. In the configuration of this fallboard opening and closing device, a connecting shaft rotatably connects a pair of hinge pieces of the hinge. A first contacting section bent into a U-shape, which is in contact with one hinge piece, is provided in one end section of this connecting shaft, and a second contacting section bent into a U-shape in the opposite direction, which is in contact with the other hinge piece, is provided in the other end section.
When the fallboard is being closed, the first contacting section and the second contacting section come into contact with the respective hinge pieces on both sides and rotate around the connecting shaft. Therefore, the connecting shaft is revolved with the rotation, and a load is applied to the fallboard with the torsion of the connecting shaft.
However, in the configuration of a conventional fallboard opening and closing device, such as this, the connecting shaft of the hinge is gradually rotated when the fallboard is being closed, and the torsion in the connecting shaft is gradually released when the fallboard is being opened. Therefore, there is a problem in that, although the movement of the fallboard can be dampened to slowly close by a load being applied thereto when the fallboard is being closed, the movement of the fallboard can not be dampened to slowly open when the fallboard is being opened because the load applied to the fallboard is merely gradually reduced.